Method of making particles having a ridge portion for use as proppant

ABSTRACT

A method for forming particles having a ridge portion includes inducing flow of a slurry of particles and a reactant through one or more orifices, detaching an amount of the slurry from the slurry flow following exit from the one or more orifices, the detached amount forming a slurry body, forming the slurry body into a particle shape, contacting the particle shaped slurry body with a coagulation solution to form a stabilized particle having the ridge portion, and drying and/or sintering the particle having the ridge portion.

BACKGROUND

Hydrocarbons (such as oil, condensate, and gas) may be produced fromwells that are drilled into formations containing them. For a variety ofreasons, such as low permeability of the reservoirs or damage to theformation caused by drilling and completion of the well, or otherreasons resulting in low conductivity of the hydrocarbons to the well,the flow of hydrocarbons into the well may be undesirably low. In thiscase, the well is “stimulated,” for example, using hydraulic fracturing,chemical (such as an acid) stimulation, or a combination of the two(often referred to as acid fracturing or fracture acidizing).

Hydraulic and acid fracturing treatments may include two stages. A firststage comprises pumping a viscous fluid, called a pad, that is typicallyfree of proppants, into the formation at a rate and pressure high enoughto break down the formation to create fracture(s) therein. In asubsequent second stage, a proppant-laden slurry is pumped into theformation in order to transport proppant into the fracture(s) created inthe first stage. In “acid” fracturing, the second stage fluid maycontain an acid or other chemical, such as a chelating agent, that canassist in dissolving part of the rock, causing irregular etching of thefracture face and removal of some of the mineral matter, which resultsin the fracture not completely closing when the pumping is stopped.Occasionally, hydraulic fracturing may be done without a highlyviscosified fluid (such as water) to minimize the damage caused bypolymers or the cost of other viscosifiers. After finishing pumping, thefracture closes onto the proppant, which keeps the fracture open for theformation fluid (e.g., hydrocarbons) to flow to the wellbore of thewell. The performance characteristics of the proppant contribute to theoverall effectiveness of the fracturing stimulation.

Proppant is typically made of materials such as sand, glass beads,ceramic beads, or other materials. Sand is used frequently as theproppant for fracture treatments. For fractures with high closurestress, such as greater than 6,000 pound per square inch (psi), in deepwells or wells with high formation forces, higher strength proppant isdesired. The closure stress which sand can sustain is normally about6,000 psi, so a closure stress over 6,000 psi would crush the sand intosmall pieces that reduces the width of the fracture and results ininsufficient conductivity for oil and/or natural gas to flow.Furthermore, as the small pieces continually flow back during theproduction, the conductivity of the wells would reduce further whichresults in a short life span of the wells or results in refracturinghaving to be performed.

Ceramic proppant has been used to maintain the conductivity of wellswith a high closure stress. Typically, the more the alumina (Al₂O₃) theproppant contains, the higher the closure stress the ceramic proppantcan withstand, but also the higher the specific gravity of the proppant.A high specific gravity may lead to fairly rapid gravitational settlingof the proppant, which results in difficulty to transport the proppantinto the fracture, especially for fractures located far from thewellbore. Also, quick settling in the fracture leads to lack of proppanton the top part of a fracture, which reduces the productivity of thewell.

High viscosity fracturing fluid, such as fluid containing a crosslinkedpolymer, may be used for transporting proppant with high specificgravity. However, fracture geometry, including width and height, is alsoaffected by the fluid viscosity. High fluid viscosity leads to a largefracture width and may make the fracture excessively grow in height intoa nonproductive or water-producing zone, impairing the efficiency ofhydraulic fracturing.

To transport proppant of high specific gravity with fracturing fluid ofa low viscosity, fiber has been added to the fluid as an additive. See,for example, U.S. Pat. No. 8,657,002, incorporated herein by referencein its entirety. To use fiber effectively for transporting proppant, theinteraction force between fiber and proppant may have significance. Forexample, while a smooth surface and good sphericity are desiredproperties of a proppant particle in order to achieve high conductivity,these properties may result in a lower interaction force with fibers,which may require the use of a greater amount of fibers and, forstimulation techniques for geological formations that rely on proppantclusters/pillars to maintain the width of a fracture and channels forconducting the formation fluid, a lower interaction force between fiberand proppant may result in an increased tendency of spreading/collapseof the clusters under closure stress, which may reduce the channel sizeand/or eliminate channels. Retaining proppant surface smoothness andsphericity while achieving good interaction force between the proppantand the fiber is thus desirable.

The so-called drip-casting manufacturing technique has been adapted forthe manufacture of spherical ceramic proppants. Drip-casting substitutesconventional ways of pelletizing (also called granulating) ceramicproppant such as using high intensity mixers and pan granulators.Vibration-induced dripping (or drip-casting) was first developed toproduce nuclear fuel pellets. See U.S. Pat. No. 4,060,497. It hassubsequently evolved into applications for metal and ceramicmicrospheres for grinding media, pharmaceuticals and food industry. Anapplication of vibration-induced dripping to aluminum oxide spheres isdescribed in U.S. Pat. No. 5,500,162. The production of the microspheresis achieved through vibration-provoked dripping of a chemical solutionthrough a nozzle. The falling drops are surrounded by a reaction gas,which causes the droplet to gel prior to entering the reaction liquid(to further gel). Using a similar approach, U.S. Pat. No. 6,197,073covers the production of aluminum oxide beads by flowing a sol orsuspension of aluminum oxide through a vibrating nozzle plate to formdroplets that are pre-solidified with gaseous ammonia before their dropinto ammonia solution. U.S. Patent Application Publication No.2006/0016598 describes the drip-casting to manufacture a high-strength,light-weight ceramic proppant. U.S. Pat. No. 8,883,693 describes theapplication of the drip-casting process to make ceramic proppant.

What is still desired, then, are ceramic proppants able to withstandhigh closure stress that have a low settling rate and high interactionforce with fiber, while having a smooth surface and good sphericity.

SUMMARY

This summary is provided to introduce a selection of concepts that arefurther described below in the detailed description. This summary is notintended to identify key or essential features of the claimed subjectmatter, nor is it intended to be used as an aid in limiting the scope ofthe claimed subject matter.

Described herein is a method for forming particles having a ridgeportion, the method including inducing flow of a slurry comprised ofparticles and a reactant through orifice(s), detaching an amount of theslurry from the slurry flow following exit from the orifice(s), thedetached amount forming a slurry body, forming the slurry body into aparticle shape, contacting the particle shaped slurry body with acoagulation solution to form a stabilized particle having the ridgeportion, and drying and/or sintering the particle having the ridgeportion.

Also described are particles having a ridge portion, wherein the ridgeportion includes a single protruding ring around an entire circumferenceof the particle, and wherein the particle has a curvature of a surfaceon one side of the protruding ring that is greater than the curvature ofa surface on an other side of the protruding ring.

Also described is a fracture treatment fluid that includes a viscousfluid and the particles having a ridge portion as described herein.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an example apparatus for carrying out a methodfor making the particles having a ridge as described herein.

FIG. 2 is a side view of the shape of the particles having a ridgeportion described herein, and further illustrates the force balance asthe slurry body floats on the surface of the coagulation solution.

DETAILED DESCRIPTION

In the following description, numerous details are set forth to providean understanding of the present disclosure. However, it may beunderstood by those skilled in the art that the methods of the presentdisclosure may be practiced without these details and that numerousvariations or modifications from the described embodiments may bepossible.

At the outset, it should be noted that in the development of any suchactual embodiment, numerous implementation—specific decisions may bemade to achieve the developer's specific goals, such as compliance withsystem related and business related constraints, which will vary fromone implementation to another. Moreover, it will be appreciated thatsuch a development effort might be complex and time consuming but wouldnevertheless be a routine undertaking for those of ordinary skill in theart having the benefit of this disclosure. In addition, the compositionused/disclosed herein can also comprise some components other than thosecited. In the summary and this detailed description, each numericalvalue should be read once as modified by the term “about” (unlessalready expressly so modified), and then read again as not so modifiedunless otherwise indicated in context. The term about should beunderstood as any amount or range within 10% of the recited amount orrange (for example, a range from about 1 to about 10 encompasses a rangefrom 0.9 to 11). Also, in the summary and this detailed description, itshould be understood that a range listed or described as being useful,suitable, or the like, is intended to include support for anyconceivable sub-range within the range at least because every pointwithin the range, including the end points, is to be considered ashaving been stated. For example, “a range of from 1 to 10” is to be readas indicating each possible number along the continuum between about 1and about 10. Furthermore, one or more of the data points in the presentexamples may be combined together, or may be combined with one of thedata points in the specification to create a range, and thus includeeach possible value or number within this range. Thus, (1) even ifnumerous specific data points within the range are explicitlyidentified, (2) even if reference is made to a few specific data pointswithin the range, or (3) even when no data points within the range areexplicitly identified, it is to be understood (i) that the inventorsappreciate and understand that any conceivable data point within therange is to be considered to have been specified, and (ii) that theinventors possessed knowledge of the entire range, each conceivablesub-range within the range, and each conceivable point within the range.Furthermore, the subject matter of this application illustrativelydisclosed herein suitably may be practiced in the absence of anyelement(s) that are not specifically disclosed herein.

The present disclosure relates to methods of making particles having aridge portion, to the particles made by the methods, and to treatmentfluids that contain the particles having a ridge portion made by themethods, wherein the particles having a ridge portion may function as,for example, proppants and/or anti-flowback additives as proppantsand/or anti-flowback additives.

While in embodiments the particles having a ridge portion are used inthe context of a treatment fluid, for example as a proppant materialand/or anti-flowback additive, it is not intended that the particleshaving a ridge portion as described herein be limited to being proppantsand/or anti-flowback additives in such treatment fluids.

As used herein, the term “treatment fluid” refers to any pumpable and/orflowable fluid used in a subterranean operation in conjunction with adesired function and/or for a desired purpose. In some embodiments, thepumpable and/or flowable treatment fluid may have any suitableviscosity, such as a viscosity of from about 1 cP to about 10,000 cP,such as from about 10 cP to about 1000 cP, or from about 10 cP to about100 cP, at the treating temperature, which may range from a surfacetemperature to a bottom-hole static (reservoir) temperature, such asfrom about 0° C. to about 150° C., or from about 10° C. to about 120°C., or from about 25° C. to about 100° C., and a shear rate (for thedefinition of shear rate reference is made to, for example, Introductionto Rheology, Barnes, H.; Hutton, J. F; Walters, K. Elsevier, 1989, thedisclosure of which is herein incorporated by reference in its entirety)in a range of from about 1 s⁻¹ to about 1000 s⁻¹, such as a shear ratein a range of from about 100 s⁻¹ to about 1000 s⁻¹, or a shear rate in arange of from about 50 s⁻¹ to about 500 s⁻¹ as measured by commonmethods, such as those described in textbooks on rheology, including,for example, Rheology: Principles, Measurements and Applications,Macosko, C. W., VCH Publishers, Inc. 1994, the disclosure of which isherein incorporated by reference in its entirety.

As used herein, a particle having a ridge portion refers to a particlehaving a transition point on the surface of the particle, whichtransition point results in a ridge portion on the surface of theparticle.

In embodiments, the transition point is an interruption in thecontinuity of the surface of the particle, which results in the particlehaving a ridged portion at the transition point. For example, thetransition point is a point where two different portions of the particlesurface meet without a smooth continuity, resulting in one portion ofthe surface protruding outwardly beyond the meeting point of the otherportion of the surface to the one portion. In embodiments, the twodifferent portions each have a different degree of curvature, and theportion with the lesser degree of curvature (i.e., the flatter curvedsurface) meets with the second portion at a point inside the radius ofcurvature of the second portion such that part of the surface of thesecond portion extends outward of the meeting point, resulting in aridge portion. In other words, if the particle were a complete sphere,the one portion with the lesser degree of curvature would (1) lie withinthe diameter of the spherical particle surface, and (2) would not extendat either end of the arc of the one portion to meet the circumference ofthe sphere based upon the diameter of the spherical particle, thusresulting in a transitional ridge at the meeting point of the twoportions. An example of this embodiment is shown in FIG. 2, thetransition points having outwardly pointing arrows extending therefrom.

In embodiments, the transition point is an excess amount of ceramicmaterial on the surface of the ceramic particle, resulting in a ridgedprotrusion of ceramic material at the transition point.

In embodiments, the ridge portion is characterized as a single ridge, orring, such as a bumper ring, extending around the entire circumferenceof the surface of the particle.

In embodiments, the particle prior to formation of the ridge portion issubstantially spherical or spheroidal, and thus these particles may bereferred to herein as substantially spherical or spheroidal particleshaving a ridge portion. By substantially spherical or spheroidal hereinis meant a particle with a fully convex boundary surface. Theseparticles may also have a substantially constant aspect ratio, which isa ratio of the diameter of the particle along a major axis to thediameter of the particle along a minor axis, for example an aspect ratioof from 0.8:1 to 1.2:1 The particles prior to formation of the ridgeportion may have other shapes as well, for example including an oblateshape or prolate shape with aspect ratios outside of the foregoingrange.

In embodiments, the method for forming particles having a ridge portioncomprises inducing flow of a slurry comprised of starting particles anda reactant through one or more orifices, detaching an amount of theslurry from the slurry flow following exit from the one or moreorifices, the detached amount forming a slurry body, forming the slurrybody into a particle shape, contacting the particle shaped slurry bodywith a coagulation solution to form a stabilized particle having theridge portion, and drying and/or sintering the stabilized particle.

In embodiments, the method further comprises forming the slurry ofparticles and reactant by mixing. As the particles, the particles may bemade of any suitable material, such as, for example, ceramic materials,sand, non-ceramic materials, composites of ceramic reinforced withadditional stronger materials and the like. As the ceramic particles ofthe slurry, any suitable ceramic material may be used, for example glassand ceramic oxides such as alumina, bauxite, aluminum hydroxide, pseudoboehmite, kaolin, kaolinite, silica, silicates, clay, talc, magnesia andmullite. The ceramic particles may include alumina-containing particlesor magnesium-containing particles. The ceramic particles may also be acomposite particle that is comprised of ceramic reinforced with higherstrength materials, which may be ceramic or non-ceramic, for examplesuch as titanium carbide, carbon nanotubes or reinforcement elementssuch as fibers or polymers. Where the particles having a ridge portionmay be used as a proppant that may need to withstand a higher fractureclosure stress, for example of 6,000 psi or more, alumina-containingparticles are desired because particles derived from alumina-containingparticles have a higher strength and toughness. Typically, the higherthe alumina (Al₂O₃) content, the higher the strength, hardness andtoughness of the particles having a ridge portion. In embodiments, theceramic particles may have an alumina content of from, for example, 5%to 95% by weight alumina, such as 20% to 75% by weight or 30% to 75% byweight.

While the starting particles may have any suitable size, an average sizeof less than 500 microns, such as an average size of 0.01 to 100 micronsor 0.01 to 50 microns, may be desirable. The starting particles (i.e.,the raw material for the end shaped particles) are desirably sizeddepending on the orifice diameter through which the slurry will pass informing the shaped particles, and the orifice diameter may be equal toor greater than, for example, ten times the raw material particleaverage diameter.

The reactant in the slurry may be any material that can be coagulated,gelled and/or cross-linked by another material that is present in thecoagulation solution. Reactants are typically organic materials used tostabilize the shape of the slurry once it is formed into the desiredparticle shape. The reactants thus react to form a stabilized solid orsemi-solid shaped product once exposed to the coagulation solution.Examples of suitable reactants include, for example, polyvinyl alcohol,polyvinyl acetate, methylcellulose, dextrin, polysaccharides such asalginates, for example sodium alginate, and molasses. Sodium alginate isa naturally occurring polysaccharide that is soluble in water as thesodium salt, and is a suitable reactant in the methods described herein.The reactant may be included in the slurry in an amount of from 0.01% to25%, such as 0.01% to 5% or 0.01% to 1% by weight of the slurry. Thesolids content of the slurry may be from, for example, 10% to 95%, suchas 15% to 90% or 20% to 90%. The solids content may be adjusted so thatthe slurry has a suitable viscosity for flow through the one or moreorifices, such as a viscosity of 1 to 10,000 cP measured at a shear rateof 100 (1/s).

The slurry may also contain one or more solvents. Possible solvents thatcan be used include water, alcohols, and ketones. Other additives mayalso be included in the slurry, such as lubricants and dispersants.Lubricants may include one or more of Manhattan fish oil, wax emulsions,ammonium stearates, and wax. Dispersants may include one or more of acolloid, polyelectrolyte, tetra sodium pyrophosphate, tetra potassiumpyrophosphate, polyphosphate, ammonium citrate, ferric ammonium citrate,hexametaphosphate, sodium silicate, ammonium polyacrylate, sodiumpolymethacrylate, sodium citrate, sodium polysulfonate orhexametaphosphate salt, as well as any surfactant.

The slurry is housed in a container that is associated with the one ormore orifices. The slurry is induced to flow from the container to theone or more orifices by any suitable method. For example, the slurry maybe induced to flow from the container by applying a load to a piston inthe container housing the slurry to force the slurry out an exit port ofthe container that is associated with the one or more orifices. Also,increasing pressure in the container housing the slurry by any suitablemethod, and/or decreasing a volume of the container housing the slurryby any suitable method, to force the slurry to exit the container at aport associated with the one or more orifices may also be used. Theslurry may also be pumped from the container housing the slurry to theone or more orifices associated with an exit of the container.

The exit port of the container may be connected to a pipe through whichthe slurry flows to the one or more orifices. Alternatively, the exitport may directly feed the slurry to the one or more orifices.

The one or more orifices may be comprised of a single orifice for makingthe shaped particles or may be comprised of multiple orifices that eachmakes shaped particles. Each orifice may be in the form of, for example,a nozzle or an opening in a membrane. Each orifice has a size thatcorrelates with an end size desired for the shaped particles. Theorifices thus may have a size of from, for example, 0.1 mm to 1 cm,depending on the approximate size desired for the end shaped particles.

The orifices are located above the coagulation solution. The apparatusmay permit the height of the orifices from the coagulation solution tobe adjusted, as the height that the slurry particles fall is a factorcontributing to the final shape of the particles.

The coagulation solution comprises a coagulant that interacts with thereactant in the slurry to coagulate, gel and/or cross-link the reactant,thereby forming the slurry into a stabilized solid or semi-solidproduct. Thus, when particle of the slurry comes into contact with thecoagulation liquid, the coagulation liquid interacts with the reactantin the slurry particle to stabilize the shape of the slurry particle.The slurry described herein is rather flowable and malleable prior tostabilization. Some examples of useful coagulation solution coagulantsinclude, for example for use with sodium alginate as a reactant, acalcium salt solution such as calcium chloride at suitable concentrationof calcium chloride, or an aluminum chloride hexahydrate solution. Theamount of coagulant to include in the solution should desirably besufficient at a minimum to coagulate, gel and/or cross-link the reactantand at a maximum should desirably not exceed the concentration that willdissolve into the solution. For example, a suitable concentration of thecoagulant in the coagulation solution may be, for example, 0.1% to 25%,such as 0.1% to 10% by weight of the coagulation solution.

The slurry may be flowed through the orifices at any desirable rate. Inembodiments, the slurry flow rate may be sufficiently slow that anamount of the slurry is able to separate from the slurry flow, after ithas passed through an orifice, as a result of its own weight, similar toa drop of water separating from a water flow out of a tap. Depending onthe viscosity of the slurry, a flow speed sufficient for this embodimentmay be, for example, from 0.01 to 1 m/s for an alumina slurry made up of75% by weight of solids and an orifice size of 0.37 mm in diameter.

In other embodiments, physical means may be used to separate the slurryinto separate particle sized slurry bodies after it has passed throughan orifice. For example, vibration energy may be applied to the one ormore orifices to separate a particle sized slurry body from the slurryflow. Application of the vibration may be controlled such that it isapplied at regular intervals based on the flow rate of the slurry inorder to sever the slurry flow at the desired points such that separateparticle sized bodies are formed. In this embodiment, the vibrationenergy is at a combination of sufficient frequency and amplitude toseparate the slurry bodies from the slurry flow. A range of frequenciesin this embodiment may be from 10-1,000 Hz for an alumina slurry made upof 75% by weight of solids and an orifice size of 0.37 mm in diameter.The vibration amplitude may be adjusted accordingly to achieve a desiredsize. The vibration action thus reduces the size of the slurry. Thevibration energy can be applied in any direction, for exampleperpendicular or parallel to the axis of the orifice.

As the separated slurry body falls from the orifice to the coagulationsolution, the slurry body transforms into the particle shape. When theslurry body falls into the coagulation solution, the reactant ispromptly coagulated, or cross-linked, by the coagulant, which forms astiff shell and stabilizes the slurry body in the particle shape.However, when the falling height between the orifices and thecoagulation solution surface is small enough, the ceramic slurry bodycannot penetrate the surface of solution due to a low kinetic energy,and thus the slurry body floats on the surface of the coagulationsolution under the force-balance of capillary force, buoyancy, andgravity, as shown in FIG. 2. The part of the particle that is submergedin the coagulation solution undergoes stabilization, whereas the part ofthe particle outside of the solution does not crosslink/stabilize,therefore making that part of the particle still flowable or malleable.The capillary force exerts the mechanical deformation that creates theridge. The falling height, defined as the distance from the orifice tothe surface of the coagulation solution, may be controlled by a heightadjuster.

In the above manner, the slurry bodies suspended on the surface of thecoagulation solution are deformed by capillary action. The top part ofthe particle that does not immediately contact the coagulation solution,and thus is not promptly stabilized, is deformed due to the kineticenergy dissipated during the impacting process. This results in theceramic particle having a ridge on its surface as detailed above. InFIG. 2, the ridge is a single ridge in the form of a ring bumper aroundthe entire circumference of the particle surface. The ridge is locatedat the point of the particle surface where the portion in thecoagulation solution and the portion floating above the coagulationsolution met. The time scale of the formation of the ridge will dependon the kinematics of the mechanical deformation for theflowable/malleable part of the particle under capillary force action.

The falling height used to achieve the slurry bodies floating on thesurface of the coagulation solution depends on the size of the endparticle, the density and the rheological properties of the slurry. Theridge on the surface of the particle can be adjusted by the controllingthe falling height, the capillary force and the density of thecoagulation solution, and the size, density and rheological propertiesof slurry body. These values should be appropriately adjusted such thatthe slurry bodies of a given slurry composition are able to attain adesired shape while falling but still float on the surface of thecoagulation solution in order to form the ridge portion. While one ofordinary skill in the art should be able to select the appropriateparameter values based on the foregoing description, the followingadditional description is given for additional guidance.

A sample slurry of 144 g water, 400 g ceramic raw powder(alumina-based), 1.6 g of sodium alginate, 0.8 g of dispersant(synthetic polyelectrolyte dispersing agent), 0.38 g of phosphate basedsurfactant and 0.48 g of lubricant (alkali-free pressing agent) wasprepared and used for illustration. The density of the slurry is 2.2g/cc, and the viscosity of the slurry at 100 (1/s) is about 300 cP. Thecoagulation solution was a 2 wt % of calcium chloride solution. Anorifice size of 0.37 mm in diameter and a flowing speed of 0.25 m/s wereemployed. The falling height was set to 2 cm. To separate the slurrybody from the orifice, a vibration frequency of 60 Hz was applied. Theparticles floated for approximately 1 min until the ridge was fullyformed. The implementation of the process herein described resulted inridged particles with a characteristic diameter of about 1 mm.

The stabilized particles having the ridge portion are collected from thecoagulation solution by any suitable methodology. The collectedstabilized particles are then dried using any suitable drying processes.For example, the stabilized particles may be subjected to air drying, orto drying using electric or gas driers. The stabilized particles mayalso be subjected to sintering, either as the drying step or as aseparate step following drying. Sintering may be conducted at atemperature of from, for example, about 800° C. to about 2,300° C., suchas from about 1,200° C. to about 1,700° C.

FIG. 1 is a schematic of an apparatus that may be used for carrying outthe above-described methods. In FIG. 1, the slurry (3) housed incontainer (2) is forced to flow by applying a load (1) on a piston. Whenthe load is applied to the slurry, the slurry is made to flow out anexit port at the bottom of the container and into tube or pipe (4) thatis connected with an orifice (5). The orifice is located above acoagulation solution (8). The slurry exits and is separated intoindividual slurry bodies (7), the separation being effected in thisapparatus through use of a mechanical device (6) that applies avibrational energy to the orifice. As the slurry bodies enter into thecoagulation solution, the bodies float on the surface of the coagulationsolution (not shown) to form stabilized particles with the ridge portion(9). The height between the nozzle and the coagulation solution surfacemay be adjusted via height adjuster (10).

The particles produced by the methods described herein may have anaverage size (based on a largest diameter) of from 0.1 mm to 1 cm, forexample from 0.1 mm to 5 mm or from 0.1 mm to 1 mm. The particles alsohave a narrow particle size distribution, for example a particle sizedistribution exhibiting differences between Dv10 and Dv90 values of lessthan 20%. The Dv-values correspond to standard percentile valuesobtained from the statistical analysis of the volume-based distribution.Dv10 is the particle size at which 10% (by volume) of the sample issmaller and 90% of the sample is larger. Similarly, Dv90 is the particlesize below which 90% of the sample distribution lies.

The particles having a ridge portion as made by the methods describedherein are able to exhibit a substantially smooth surface.

Where the particles having a ridge portion are used in a treatmentfluid, for example as proppant, the defined ridge of the particlesdescribed herein may increase the interlocking ability/friction force ofthe particles with fibers by creating a defined high stress area(associated with the ridge) that latches onto the fibers, which couldincrease the capability of the fiber to transport the particles into thefracture during the fracturing treatment. This fiber-particleinterlocking mechanism also could increase the strength of pillars whena fracture closes onto the pillars. Also, the conductivity of theproppant pack is not, or is minimally, compromised because thesubstantially smooth surface of the particles may minimize friction andturbulence of produced fluid/gases over the production. The definedridge also may increase the friction force between the walls of thefracture and the particles, which decreases the settling of theparticles in the fracture and increases the strength of the pillars. Inaddition, the particles having a ridge portion as described herein maybe harder to flow back compared to spherical proppant. The particles canbe used together with other shaped proppants as an anti-flowbackadditive. The particles can also be used together with fiber to achieveenhanced anti-flowback control.

In some embodiments, the concentration of the shaped particles in thetreatment fluid may be any desired value, such as a concentration in therange of from about 0.01 to about 80% by weight of the treatment fluid,or a concentration in the range of from about 0.1 to about 25% by weightof the treatment fluid, or a concentration in the range of from about 1to about 10% by weight of the treatment fluid.

Although the shaped particles may be used by themselves in the treatmentfluid, for example as proppants for a fracture, they may also be usedtogether with conventional proppants, for example with sphericalproppant particles of glass, sand, ceramic and the like. Other proppantparticles may be used in a weight ratio of the shaped particles to theother proppant particles of from 0.1:1 to 10:1. In some embodiments,other proppants may include sand, synthetic inorganic proppants, coatedproppants, uncoated proppants, resin coated proppants, and resin coatedsand. The proppants may be natural or synthetic (including silicondioxide, sand, nut hulls, walnut shells, bauxites, sintered bauxites,glass, natural materials, plastic beads, particulate metals, drillcuttings, ceramic materials, and any combination thereof), coated, orcontain chemicals; more than one may be used sequentially or in mixturesof different sizes or different materials. The proppant may be resincoated. The particles having a ridge portion may also be resin coated,where desired.

In some embodiments, the treatment fluids may also include a fibrousmaterial, as well known in the art. Fibers may be included in thetreatment fluid in order to assist in transport of proppants into thefractures. For example, the treatment fluid may comprise the particleshaving a ridge portion, optionally with substantially spherical orspheroidal particles, and a fiber of any desired thickness (diameter),density and concentration that is effective to assist in the downholeoperation. The fibers may be one or more member selected from naturalfibers, synthetic organic fibers, glass fibers, ceramic fibers, carbonfibers, inorganic fibers, metal fibers, a coated form of any of theabove fibers.

Fibers may be used in bundles. The fibers may have a length in the rangeof from about 1 mm to about 30 mm, such as in the range of from about 5mm to about 20 mm. The fibers may have any suitable diameter or crossdimension (shortest dimension), such as a diameter of from about 5 to500 microns, or a diameter of from about 20 to 100 microns, and/or adenier of from about 0.1 to about 20, or a denier of from about 0.15 toabout 6.

The fibers may be formed from a degradable material or a non-degradablematerial. The fibers may be organic or inorganic. Non-degradablematerials are those wherein the fiber remains substantially in its solidform within the well fluids. Examples of such materials include glass,ceramics, basalt, carbon and carbon-based compound, metals and metalalloys. Polymers and plastics that are non-degradable may also be usedas non-degradable fibers. Such polymers and plastics that arenon-degradable may include high density plastic materials that are acidand oil-resistant and exhibit a crystallinity of greater than 10%.Degradable fibers may include those materials that can be softened,dissolved, reacted or otherwise made to degrade within the well fluids.Such materials may be soluble in aqueous fluids or in hydrocarbonfluids.

Suitable fibers may also include any fibrous material, such as, forexample, natural organic fibers, comminuted plant materials, syntheticpolymer fibers (by non-limiting example polyester, polyaramide,polyamide, novoloid or a novoloid-type polymer), fibrillated syntheticorganic fibers, ceramic fibers, inorganic fibers, metal fibers, metalfilaments, carbon fibers, glass fibers, ceramic fibers, natural polymerfibers, and any mixtures thereof.

The treatment fluid includes a carrier solvent that may be a puresolvent or a mixture. Suitable solvents may be aqueous or organic based.For example, the treatment fluid may include a carrier solvent and thesubstantially spherical or spheroidal particles. The fluid may be anysuitable fluid, such as, for example, water, fresh water, producedwater, seawater, or an aqueous solvent, such as brine, mixtures of waterand water-soluble organic compounds and mixtures thereof. Other suitableexamples of fluids include hydratable gels, such as guars,poly-saccharides, xanthan, hydroxy-ethyl-cellulose; cross-linkedhydratable gels, viscosified acid, an emulsified acid (such as with anoil outer phase), an energized fluid (including, for example, an N₂ orCO₂ based foam), and an oil-based fluid including a gelled, foamed, orotherwise viscosified oil. Suitable organic solvents that may act as acarrier solvent for the treatment fluids of the disclosure include, forexample, alcohols, glycols, esters, ketones, nitrites, amides, amines,cyclic ethers, glycol ethers, acetone, acetonitrile, 1-butanol,2-butanol, 2-butanone, t-butyl alcohol, cyclohexane, diethyl ether,diethylene glycol, diethylene glycol dimethyl ether,1,2-dimethoxy-ethane (DME), dimethylether, dibutylether, dimethylsulfoxide (DMSO), dioxane, ethanol, ethyl acetate, ethylene glycol,glycerin, heptanes, hexamethylphosphorous triamide (HMPT), hexane,methanol, methyl t-butyl ether (MTBE), N-methyl-2-pyrrolidinone (NMP),nitromethane, pentane , petroleum ether (ligroine), 1-propanol,2-propanol, pyridine, tetrahydrofuran (THF), toluene, triethyl amine,o-xylene, m-xylene, p-xylene, ethylene glycol monobutyl ether,polyglycol ethers, pyrrolidones, N-(alkyl or cycloalkyl)-2-pyrrolidones,N-alkyl piperidones, N, N-dialkyl alkanolamides, N,N,N′,N′-tetra alkylureas, dialkylsulfoxides, pyridines, hexaalkylphosphoric triamides,1,3-dimethyl-2-imidazolidinone, nitroalkanes, nitro-compounds ofaromatic hydrocarbons, sulfolanes, butyrolactones, alkylene carbonates,alkyl carbonates, N-(alkyl or cycloalkyl)-2-pyrrolidones, pyridine andalkylpyridines, diethylether, dimethoxyethane, methyl formate, ethylformate, methyl propionate, acetonitrile, benzonitrile,dimethylformamide, N-methylpyrrolidone, ethylene carbonate, dimethylcarbonate, propylene carbonate, diethyl carbonate, ethylmethylcarbonate, dibutyl carbonate, lactones, nitromethane, nitrobenzenesulfones, tetrahydrofuran, dioxane, dioxolane, methyltetrahydrofuran,dimethylsulfone, tetramethylene sulfone, diesel oil, kerosene,paraffinic oil, crude oil, liquefied petroleum gas (LPG), mineral oil,biodiesel, vegetable oil, animal oil, aromatic petroleum cuts, terpenes,mixtures thereof.

Treatment fluids may optionally comprise other chemically differentmaterials. In embodiments, the treatment fluid may further comprisestabilizing agents, surfactants, diverting agents, or other additives.Additionally, a treatment fluid may comprise a mixture of variouscrosslinking agents, and/or other additives, such as fibers or fillers.Furthermore, the treatment fluid may comprise buffers, pH controlagents, and various other additives added to promote the stability orthe functionality of the treatment fluid. The components of thetreatment fluid may be selected such that they may or may not react withthe subterranean formation that is to be treated.

In some embodiments, the treatment fluid may further have a viscosifyingagent. The viscosifying agent may be any crosslinked polymers. Thepolymer viscosifier can be a metal-crosslinked polymer. Suitablepolymers for making the metal-crosslinked polymer viscosifiers include,for example, polysaccharides such as substituted galactomannans, such asguar gums, high-molecular weight polysaccharides composed of mannose andgalactose sugars, or guar derivatives such as hydroxypropyl guar (HPG),carboxymethylhydroxypropyl guar (CMHPG) and carboxymethyl guar (CMG),hydrophobically modified guars, guar-containing compounds, and syntheticpolymers. Crosslinking agents based on boron, titanium, zirconium oraluminum complexes are typically used to increase the effectivemolecular weight of the polymer and make them better suited for use inhigh-temperature wells.

Other suitable classes of polymers that may be used as a viscosifyingagent include polyvinyl polymers, polymethacrylamides, cellulose ethers,lignosulfonates, and ammonium, alkali metal, and alkaline earth saltsthereof. Additional examples of other water soluble polymers that may beused as a viscosifying agent include acrylic acid-acrylamide copolymers,acrylic acid-methacrylamide copolymers, polyacrylamides, partiallyhydrolyzed polyacrylamides, partially hydrolyzed polymethacrylamides,polyvinyl alcohol, polyalkyleneoxides, other galactomannans,heteropolysaccharides obtained by the fermentation of starch-derivedsugar and ammonium and alkali metal salts thereof.

In some embodiments, the carrier fluid may optionally further compriseadditional additives, including, for example, acids, fluid loss controladditives, gas, corrosion inhibitors, scale inhibitors, catalysts, claycontrol agents, biocides, friction reducers, combinations thereof andthe like. For example, in some embodiments, it may be desired to foamthe composition using a gas, such as air, nitrogen, or carbon dioxide.

Although the preceding description has been set forth with reference toparticular means, materials and embodiments, it is not intended to belimited to the particulars disclosed herein; rather, it extends to allfunctionally equivalent structures, methods and uses, such as are withinthe scope of the appended claims. Furthermore, although only a fewexample embodiments have been described in detail above, those skilledin the art will readily appreciate that many modifications are possiblein the example embodiments without materially departing from thedisclosure herein. Accordingly, all such modifications are intended tobe included within the scope of this disclosure as defined in thefollowing claims. In the claims, means-plus-function clauses areintended to cover the structures described herein as performing therecited function and not only structural equivalents, but alsoequivalent structures. Thus, although a nail and a screw may not bestructural equivalents in that a nail employs a cylindrical surface tosecure wooden parts together, whereas a screw employs a helical surface,in the environment of fastening wooden parts, a nail and a screw may beequivalent structures.

1. (canceled)
 2. (canceled)
 3. (canceled)
 4. (canceled)
 5. (canceled) 6.(canceled)
 7. (canceled)
 8. (canceled)
 9. (canceled)
 10. (canceled) 11.(canceled)
 12. (canceled)
 13. (canceled)
 14. Particles having a ridgeportion, wherein the ridge portion comprises a single ring around anentire circumference of the particle, wherein the ridge portion has anaverage size of from 0.1 mm to 1 cm, and the ridge portion has acurvature of a surface on one side of the ring that is greater than thecurvature of a surface on an other side of the ring.
 15. (canceled) 16.The particles according to claim 14, wherein if the particles having theridge portion were completely spherical, the surface on the one side ofthe ring would lie within the diameter of the sphere and an arc lengthof the surface on the one side would be such that either end of the arcwould not extend to meet the circumference of the sphere.
 17. A fracturetreatment fluid comprising a viscous fluid and the particles of claim14.
 18. The fracture treatment fluid according to claim 17, furthercomprising fibers.
 19. The fracture treatment fluid according to claim17, further comprising proppant particles.